Identify the correct statement(s), regarding the...

Identify the correct statement(s), regarding the chlorination of alkanes. (a) The relative rates of abstraction of tertiary, secondary and primary hydrogen atoms are in the ratio $5.0: 3.8: 1$ respectively.s (b) The more reactive chlorine radical is less selective. (c) The reaction proceeds through homolytic cleavage. (d) When n-butane is chlorinated, the product formed is $\mathrm{CH}_{3} \mathrm{CHClCH}_{2} \mathrm{CH}_{3}$ exclusively as the secondary hydrogen is more readily displaced.

Identify the correct statement(s), regarding the chlorination of alkanes.
(a) The relative rates of abstraction of tertiary, secondary and primary hydrogen atoms are in the ratio $5.0: 3.8: 1$ respectively.s
(b) The more reactive chlorine radical is less selective.
(c) The reaction proceeds through homolytic cleavage.
(d) When n-butane is chlorinated, the product formed is $\mathrm{CH}_{3} \mathrm{CHClCH}_{2} \mathrm{CH}_{3}$ exclusively as the secondary hydrogen is more readily displaced.

Key Concepts

Homolytic Cleavage

Homolytic cleavage refers to the process of breaking a chemical bond such that each of the bond's electrons is distributed equally to the two resulting fragments, forming radicals. In the context of halogenation, this is the primary step where the halogen molecule splits into two halogen radicals, initiating the radical chain mechanism required for the reaction to proceed.

Reactivity versus Selectivity of Radicals

This key concept discusses the balance between how reactive a radical species is and how selective it is in attacking particular bonds. Highly reactive radicals like chlorine are less discriminative, meaning they react with various hydrogen types almost indiscriminately, whereas less reactive radicals such as bromine display greater selectivity. This difference influences the distribution of products in halogenation reactions.

Radical Halogenation Reaction Mechanism

This concept covers the overall process by which alkanes undergo halogenation via a chain reaction mechanism. It involves the initiation step where a halogen molecule undergoes homolytic cleavage to produce two radicals, followed by propagation steps where these radicals abstract hydrogen atoms from alkanes to generate alkyl radicals, which then react with halogen molecules to produce the halogenated product and another halogen radical. Termination steps involve the combination of radicals, ending the chain reaction.

Hydrogen Abstraction and Relative Reactivity

In radical halogenation, different types of hydrogen atoms (primary, secondary, and tertiary) are abstracted at different rates. This concept highlights that tertiary hydrogen atoms typically are more reactive than secondary, which in turn are more reactive than primary hydrogens due to the stability of the resulting alkyl radicals. The relative abstraction rates determine which sites on the alkane are more likely to be attacked during the reaction.

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